I wonder if the track even knew the full story when the payouts were posted. I'm not a computer guy, but I'd guess that the tote company's computers have an algorithm to determine whether a jackpot should be paid out. They probably store each ticket as a bunch of sequences and then compare all those sequences with the winning sequence(s). In this case, the dead heat resulted in two winning sequences (which could also happen when there are late scratches in a race won by a favorite), both of which were hit. Ergo no jackpot.

Perhaps in a fairer world the algorithm would also check to see if all the winning combinations were on a single ticket, but I doubt fairness was top of mind when jackpot bets were created.